It is known to make micromechanical mirror structures (or reflectors), at least in part, of semiconductor materials and obtain employing MEMS (Micro-Electro-Mechanical Systems) technology.
MEMS reflectors are designed to receive an optical beam and to vary the direction of propagation thereof, in a periodic or quasi-periodic way. For this purpose, MEMS reflectors include mobile elements formed by mirrors, the positions of which in space are controlled electrically by appropriate oscillation control signals.
In greater detail, in a generic MEMS reflector comprising a respective mirror, control of the position of the mirror is of particular importance to enable scanning of a portion of space with an optical beam, which is made to impinge on the mirror. In particular, control of the position of the mirror determines in the case of resonant MEMS reflectors, where, in use, the mirror is made to oscillate in a substantially periodic way about a resting position, the period of oscillation being as close as possible to the resonance frequency of the mirror in order to maximize the angular distance covered by the mirror during each oscillation, and thus maximize the extent of the portion of space scanned.
For instance, United States Patent Application Publication No. 2011/0109951 (incorporated by reference) describes a circuit to control of the position of the mirror of a MEMS reflector of a resonant type, said mirror being set for turning, under the action of an actuator of an electrostatic type, about an axis of rotation. In particular, the MEMS reflector disclosed therein comprises a fixed supporting body, made of semiconductor material, and a mirror, which is constrained to the fixed supporting body by torsional springs. An actuator of an electrostatic type typically requires high operating voltages, higher than 150 V or currents in the region of 100 mA, thus limiting the energy efficiency of the final device.
There is a need in the art to provide an oscillating structure with reduced energy consumptions and, at the same time, optimized electromechanical efficiency.